1. Field of the Invention
The present invention relates generally to filament payout apparatus, and, more particularly, to such apparatus as utilized in a missile for establishing a data link.
2. Description of Related Art
In a number of missiles, at launch an extent of a filament (e.g., wire or optical fiber) is payed out from the missile and interconnected with apparatus at launch site to provide a data link over which commands and navigational information are communicated. Especially if the filament consists of an optical fiber, it is important in paying out the fiber not to produce kinking or induce undue stress in the fiber since this may result in breakage, or, at the least, reduce the transmission quality.
A commonly employed form of payout apparatus consists of a generally drum-like member or canister fixedly mounted onto the missile with the filament helically wound about an axis parallel to the longitudinal axis of the missile. The drum, or canister, is immovable with respect to the missile so that as the fiber unwinds it results in an extended helix. This manner of payout produces a twist in the fiber which has been found to provide optical signal loss. In addition, there are some programs which require that the fiber not coil when it goes slack (i.e., that portion payed out from the vehicle) since the fiber could break if tension were suddenly applied.
Also, on these prior canisters the filament is wound in a helix at approximately 60 degrees to the direction of payout which means that there is a peel point at which the fiber is removed from the canister pack experiencing a substantial angular deformation. At this peel point the winding pack experiences a radial force with a direction toward the center of the pack and a magnitude that increases with the square of the vehicle velocity. It is desirable to reduce this radial force by rotating the canister, thereby, counteracting the velocity squared term. This radial force tends to disturb winding pack stability and can produce a failure mode known as "pop up".
Also, in the prior canisters, it has been found advisable to provide the canister with a decided taper from the forward to the aft end in order to reduce frictional force of the fiber on underlying layers as it is removed from the pack.